Recently, the increasing demand for computers has caused the industries in the field of memory devices to develop rapidly. The market has demanded products of higher performance and lower costs, which leads to a fierce competition on the supply side that has been trying to meet the demand. One of the significant factors in determining the performance of a computer is a storage device, and the mainstream of the same is a semiconductor memory configured so that memory cells are formed on a semiconductor substrate such as silicon. The main requirements for the high performance of the semiconductor memory are “high speed of input/output to/from memory”, “large capacity of memory”, and “stability of storage.” Computers comprising storage devices including silicon based electronics may have various configurations to meet various demands of the market, but in the case where both higher speed and larger capacity are pursued, the cost rises.
Worldwide sale of stand-alone and embedded solid state microelectronic memory is approximately $65 billion/year. Existing microelectronic memory is either fast and temporary (for example, DRAM) or slow and permanent (for example, magnetic storage). DRAM must be refreshed more than 10 times per second, with attendant power and overhead requirements. Non-volatile memory is not amenable to integration with microelectronic circuits, with the exception of “flash” memory, which has a limited number of write/erase cycles and requires high voltage (greater than 15 V) to operate. Flash memory (generally has a cycle life of approximately 10000 write/erase cycles) is significantly slower than DRAM, although it has good retention (greater than 10 yrs). In addition, flash memory has reliability problems with increasing density, due to crosstalk and limited cycle life. The less than 100 milli-second retention of DRAM is tolerated due to its high density, speed, and endurance, but longer retention could significantly reduce power consumption and broaden applications.
Important drawbacks of silicon based electronics are their rigidity and requirement of high temperature for fabrication. These properties impede their applications as devices on flexible substrates such as plastics, cloths, and papers. Printed electronics on flexible surfaces is projected to be the growth areas for future electronics with values of approximately $25 billion/year by 2015. The active component of organic and plastic based electronic devices is inherently flexible and can readily be adapted to a printing process. Thus, there is a need for a non-volatile memory with significantly reduced power consumption, faster write/erase speed, longer cycle life than Flash, and low manufacturing cost.